From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v5 6/9] KVM: MMU: introduce pte_prefetch_topup_memory_cache() Date: Tue, 13 Jul 2010 08:35:33 +0300 Message-ID: <4C3BFB25.2010602@redhat.com> References: <4C330918.6040709@cn.fujitsu.com> <4C330A37.8080709@cn.fujitsu.com> <4C39C1AB.6000606@redhat.com> <4C3A8694.1000401@cn.fujitsu.com> <4C3B09FD.3060307@redhat.com> <4C3BBE84.30708@cn.fujitsu.com> <4C3BE9BD.40007@redhat.com> <4C3BEAC3.9000501@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Xiao Guangrong Return-path: In-Reply-To: <4C3BEAC3.9000501@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 07/13/2010 07:25 AM, Xiao Guangrong wrote: > >> Regressions? no. Or do you mean the problem already exists? Where? >> > I mean this is a exist problem, likes invlpg, pte-write and sync-page, there are > speculative path that it's not real access, but marked dirty if pte is writable. > Right. We should fix those too. Prefetch is much more worrying though, especially with ept. If a guest is using just 1/8 of the pages, it can look to migration as if it's using 100% of the pages. The impact can be pretty large. In contrast, I'm not too worried about invlpg, as most times an access will follow a miss, and usually a write access if we set a writeable pte. Not sure about sync-page. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.